Path to the file being executed. In the global scope it constains the filename which is currently being executed,
<repl> if running in the REPL, <stdin> if code is being read from stdin, or <eval> if evaluating
code straight from the CLI. Inside a module, it contains the absolute path to the module file.

Relative paths are resolved relative to the calling module, or the module which contains the call to
require().

Regular module ids are resolved by looking into the system paths in system.path. The list of paths
to search for modules is dynamic and can be modified at runtime. The following are the builtin system paths: